After that announcement, the Chief Justice of the California Supreme Court said that enforcing federal laws at the local level is a threat to the rule of law, or something:

California Supreme Court Chief Justice Tani G. Cantil-Sakauye did not mention President Trump by name in her annual State of the Judiciary speech Monday, but she blasted federal actions on immigration and warned that the rule of law in the state is under threat.
[…]
“Simply put, the rule of law means that we as a people are governed by laws and rules, not by a monarch,” she said.

People take the rule of law for granted until it is under threat, she added.

“I submit to you today that the rule of law is being challenged,” she said. “We are living in a time of civil rights unrest, eroding trust in our institutions, economic anxiety and unprecedented polarization.”

Justice Cantil-Sakauye, a Republican who was nominated in 2010 by then-Gov. Arnold Schwarzenegger, said she’s not necessarily against enforcing those federal laws, but argued that… well here, read it for yourself:

She argued that sweeps by immigration authorities had already created tension between the judicial branch and government agencies. Courthouses, she said, should be treated like hospitals or churches – places where immigration enforcement is “the exception, not the practice.”

Cantil-Sakauye told legislators: “I am not saying, ‘Do not enforce the federal law.’ I am saying, ‘Please don’t do so at, or in, California state courthouses.'”